JP2017154181A - Casting with first metal component and second metal component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved casting method and casting molds for three-dimensional components having intricate internal voids.SOLUTION: The present disclosure generally relates to casting molds including a casting core comprising a first metal component and a second metal component. In an aspect, the first metal component has a lower melting point than the second metal component. In another aspect, the second metal component surrounds at least a portion of the first metal component and defines a cavity in the casting core when the first metal component is removed and the second metal component is not removed.SELECTED DRAWING: Figure 4

Description

  The present disclosure generally relates to a casting core (core) part and a process using the casting core part. The core component of the present invention can include one or more first metal components and one or more second metal components. The first metal part and the second metal part provide useful properties in casting operations, such as casting of jet aircraft engine turbine blades or superalloys used to produce power generation turbine parts.

  Many modern engines and next-generation turbine engines require components and components with intricate and complex geometries. These geometries require new types of materials and manufacturing techniques. Engine parts and conventional techniques for manufacturing engine parts require a cumbersome process called investment casting or lost wax casting. An example of investment casting relates to the manufacture of typical rotor blades used in gas turbine engines. Turbine blades typically include a hollow airfoil that has at least one air inlet for receiving compressed cooling air during operation in the engine. A radial flow path extending along the line. The various cooling passages in the blade include a serpentine flow path located in the middle of the airfoil between the leading and trailing edges. The airfoil typically includes an air inlet that extends through the blade for receiving compressed cooling air. This air inlet has local features such as short turbulator ribs or short turbulator pins to enhance heat transfer between the heated sidewalls of the airfoil and the internal cooling air. Have.

  The manufacture of these turbine blades, usually manufactured from high strength superalloy metal materials, requires many steps. First, a precision ceramic core is produced that matches the desired intricate cooling passages in the turbine blade. A precision mold or mold is also created that defines the precise three-dimensional outer surface of the turbine blade, including the turbine blade airfoil, platform, and integral dovetail. The ceramic core is assembled inside the two mold halves, which form a space or void between them that defines the metal part of the resulting blade. Wax is injected into the assembled mold to fill the void and enclose the ceramic core encapsulated within the mold. The two mold halves are divided and removed from the molded wax. The molded wax has the precise configuration of the desired blade and is then coated with a ceramic material to form the surrounding ceramic shell. The wax is then melted and removed from the shell, leaving a corresponding void or space between the ceramic shell and the internal ceramic core. The molten superalloy metal is then poured into the shell, filling the void in the shell and re-encapsulating the ceramic core contained within the shell. The molten metal is cooled and solidified, after which the outer shell and inner core are properly removed, leaving the desired metal turbine blade with the cooling passages cast therein.

  The cast turbine blade may then be subjected to additional post-cast modifications. Additional post-cast modifications include drilling the film cooling holes through the airfoil sidewalls in appropriate rows, as desired to provide an outlet for cooling air flowing through the interior. The cooling air, but not limited thereto, then forms a protective cooling air film or cooling air blanket on the outer surface of the airfoil during operation within the gas turbine engine. However, these post-cast modifications are limited and are more complex given the continued complexity of turbine engines and the perceived efficiency of some cooling circuits within the turbine blades. Intricate internal geometry needs to be requested. While it is possible to manufacture these parts by investment casting, positional accuracy and complicated internal geometry are more complex to manufacture using these conventional manufacturing processes. Accordingly, it would be desirable to provide an improved casting method for 3D parts having intricate internal voids.

  Precision metal casting using hybrid core parts using a combination of refractory metal cast parts and ceramic cast parts is known in the art. Hybrid cores are manufactured that include a refractory metal portion and a ceramic material portion. See, for example, US Patent Application Publication No. 2013/0266816 entitled “Additive manufacturing of hybrid core”. The technology disclosed in the above specification and used to manufacture the hybrid core used conventional powder bed technology. While the hybrid core provides additional flexibility for superalloy casting, for example in the casting of turbine blades used in jet aircraft engines, there remains a need for more advanced core investment casting techniques.

US Patent Application Publication No. 2015/0203411

  The present disclosure generally relates to a mold that includes a casting core comprising a first metal part and a second metal part. In one aspect, the first metal part may have a lower melting point than the second metal part. In another aspect, the second metal part surrounds at least a portion of the first metal part and defines a cavity in the casting core when the first metal part is removed. One or more of the first metal part and / or the second metal part can be formed by an additive manufacturing process using the advanced methods of direct laser melting and / or direct laser sintering described herein. The casting core may further comprise an outer shell mold formed from a ceramic material.

  In exemplary embodiments, the first metal component may include aluminum, copper, silver, and / or gold, and the second metal component may include molybdenum, niobium, tantalum, and / or tungsten. . Furthermore, the first metal part and / or the second metal part may include an alloy.

  One or more of the first metal part and / or the second metal part is adapted to define a structure in the cast part, in particular, a cooling hole, a cooling channel at the rear edge, or a micro channel. be able to. The first metal part and / or the second metal part can also be adapted to provide a core support structure, a platform core structure, or a tip flag structure. Multiple metal parts, non-refractory metals and / or refractory metals, may be used in a single casting core, or may be used alone in a ceramic casting core assembly or other It may be used with cast parts.

  The present invention is also a method of manufacturing a cast part by removing a first metal part from a mold assembly comprising a first metal part and a second metal part to form a cavity in the mold assembly. Removing the first metal part having a lower melting point than the second metal part; pouring molten metal into at least a portion of the cavity to form a cast part; and Removing from the cast part.

  In another aspect, the entire casting core including the first metal part and the second metal part can be produced from the powder bed by direct laser melting and / or direct laser sintering. Alternatively, the first metal part and the second metal part may be assembled in a mold and a ceramic slurry may be introduced to produce a casting core.

  In another aspect, the first metal part and the second metal part may be formed simultaneously using an AM process. In one embodiment of a possible AM process, the first metal part and the second metal part are (a) irradiated binder injection of a powder layer of a powder bed to form a fused / sintered region. Consolidating and / or sintering by: (b) providing a subsequent powder layer on the powder bed; (c) corresponding to at least the first metal component and the second metal component; Each layer can be formed by a process that includes repeating steps (a) and (b) using two or more different powder compositions.

It is the schematic which shows the example of the conventional apparatus for additional manufacture. It is a perspective view of the additional manufacturing apparatus which enables manufacture of the component which has a different composition in the whole molding. It is a top view of the components manufactured using the addition manufacturing apparatus of FIG. FIG. 3 illustrates a method for forming a cast part, in accordance with one embodiment of the present invention. FIG. 3 illustrates a method for forming a cast part, in accordance with one embodiment of the present invention. FIG. 3 illustrates a method for forming a cast part, in accordance with one embodiment of the present invention. FIG. 3 illustrates a method for forming a cast part, in accordance with one embodiment of the present invention. FIG. 3 illustrates a method for forming a cast part, in accordance with one embodiment of the present invention.

  The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations capable of implementing the concepts described herein. Absent. The detailed description includes specific details that are intended to provide a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details.

  The first metal part and / or the second metal part of the present invention can be manufactured using an additive manufacturing (AM) process. The AM process generally involves accumulating one or more materials to form a net shape or near net shape (NNS) object, as opposed to a removal manufacturing method. “Additional manufacturing” is an industry standard term (ASTM F2792), but AM encompasses a variety of manufacturing and prototyping techniques known by various names including freeform, 3D printing, rapid prototyping / rapid tooling, etc. To do. AM technology can mold complex parts from a wide range of materials. In general, a self-supporting object can be formed from a computer aided design (CAD) model. A particular type of AM process uses a beam of energy, such as an electron beam or electromagnetic radiation such as a laser beam, to sinter or melt the powder material to create a solid three-dimensional object. In a solid three-dimensional object, particles of powder material are adhered to each other. For example, different material systems such as engineering plastics, thermoplastic elastomers, metals and ceramics are used. Laser sintering or laser melting is a notable AM process because it rapidly forms functional prototypes and functional tools. Applications include the direct production of complex workpieces, investment casting molds, metal molds for injection molding and die casting, and molds and cores for sand casting. Prototype molding is another common use of the AM process to improve concept transfer and testing during the design cycle.

  Selective laser sintering, direct laser sintering, selective laser melting, and direct laser melting produce three-dimensional (3D) objects by sintering or melting fine powders using a laser beam. It is a general industrial term used to refer to. For example, US Pat. No. 4,863,538 and US Pat. No. 5,460,758 describe conventional laser sintering techniques. More precisely, sintering involves fusing (aggregating) the particles of the powder at a temperature below the melting point of the powder material, while melting completely melts the particles of the powder and makes it hard and homogeneous. With the formation of lumps. The physical processes associated with laser sintering or laser melting include heat transfer to the powder material followed by sintering or melting of the powder material. While laser sintering and laser melting processes can be applied to a wide range of powder materials, the scientific and technical aspects of the manufacturing path are not well understood. Scientific and technical aspects of the manufacturing path are, for example, the sintering or melting rate, and the effect of processing parameters on the formation of microstructures during the laminate manufacturing process. This molding method involves multiple aspects of heat transfer, mass transfer, and momentum transfer, as well as chemical reactions, thereby making the process very complex.

  FIG. 1 is a schematic diagram showing a cross section of an exemplary conventional system 100 for direct metal laser sintering (DMLS) or direct metal laser melting (DMLM). The apparatus 100 is a method of forming layer by layer by sintering or melting a powder material (not shown) using an energy beam 136 emitted from a source such as a laser 120, for example. An object such as the part 122 is formed. Powder melted by the energy beam is supplied by the reservoir 126 and spread evenly on the build plate 114 using the recoater arm 116 moving in the direction of 134. The recoater arm 116 maintains the powder at a constant height 118 and removes excess powder material beyond the powder height 118 into the waste container 128. The energy beam 136 sinters or melts the cross-sectional layer of the object being molded under the control of the galvo scanner 132. The build plate 114 is lowered and another layer of powder is spread over the build plate and the object being molded, after which the laser 120 performs the next powder melting / sintering. This process is repeated until the part 122 is molded from the molten / sintered powder material. The laser 120 may be controlled by a computer system that includes a processor and memory. The computer system can determine the scan pattern of each layer and can control the laser 120 to irradiate the powder material according to the scan pattern. After completion of the molding of the part 122, various post-processing procedures can be applied to the part 122. The post-treatment procedure includes the removal of excess powder, for example by blowing or sucking. Another post-processing procedure includes a stress relief process.

  The conventional laser melting / sintering techniques described above have several limitations with respect to producing AM objects with various compositions. For example, it is possible to change the composition of the powder between successive layers, but the change can be cumbersome, especially in industrial situations where the interruption time between manufacturing steps is costly. Recently, a more advanced laser melting method / laser that allows precise control of the composition of the molding not only between successive powder layers of the molding, but also horizontally within the same powder layer. A sintering method has been developed. See U.S. Patent Application Publication No. 2014/834517, filed August 25, 2015, entitled “Coater Apparatus and Method for Additive Manufacturing”. This specification is incorporated herein by reference in its entirety.

  As shown in FIG. 2, the advanced powder bed machine includes a reservoir assembly 30 disposed on a dispenser 32. The dispenser 32 has one or more elongated troughs 38A-38E. The elongated trough includes a deposition valve (binary or variable) between the trough and the build plate that controls the deposition of powder on the build plate 12.

  The reservoir assembly 30 includes one or more reservoirs disposed on each trough 38A-38E. As shown in FIG. 2, the reservoir assembly includes, for example, 20 reservoirs. Each reservoir is defined by an appropriate wall or partition to form a volume that is effective for storing and discharging powder, generally indicated by “P” (ie, P1, P2, P3, etc.). To do. Each individual reservoir may contain a powder P having unique properties, such as composition and / or particle size of the powder. For example, P1 can be used to mold part 60, P2 can be used to mold part 62, and P3 can be used to mold part 64. It will be appreciated that the powder P may be any material suitable for additive manufacturing. For example, the powder P may be a metal powder, a polymer powder, an organic powder, or a ceramic powder. Note that the reservoir assembly 30 is optional and the powder P may be placed directly into the trough 38.

  Optionally, it may be desirable to empty the troughs 38A-38E between process cycles, for example, where it is desired to deposit a different mixture of powders than in past cycles. is there. Emptying can be accomplished by moving the troughs 38A-38E over the excess powder container 14 and opening the deposition valve to discard the excess powder. This process may be enhanced by flowing a gas or mixture of gases through troughs 38A-38E.

  FIG. 3 shows a half of the powder layer of the component C subdivided into a grid with a width of 10 elements and a height of 15 elements. The size of the grid elements and the spacing between the elements are emphasized for the sake of clarity. The representation of part C as a continuous layer, each with a grid of elements, can be modeled using, for example, suitable solid modeling or computer aided design software. Each unique diagonal pattern shown in FIG. 4 represents one unique powder characteristic (eg, composition and / or particle size). As shown, a single powder layer may include different types of powders (eg, P1, P2, and P3). Although three different types of powder are shown in FIG. 3, more or fewer types of powders may be used without departing from the scope of the present disclosure. Will be understood.

  This cycle of applying the powder P and then laser melting the powder P is repeated until the entire part C is completed.

  Other techniques may be used to provide a core component according to the present invention. For example, the parts may be manufactured using injection molding techniques that use different materials within the same core part.

  The core component of the present disclosure includes a cooling hole, a trailing edge cooling channel, a micro channel, a cross hole connecting two cooling cavities, a double wall or a cooling structure near the wall. It can be used to provide cooling functions, such as internal impingement holes, refresher holes formed in the base turn of the blade, and additional cooling functions known in the art. Further, the core component can be used to reconcile the thermal expansion characteristics of two or more materials. The core component of the present disclosure may also be used to add or dope a desired element or a desired alloy to some areas of a cast metal object.

  The additive manufacturing techniques described above allow the formation of core parts of almost any desired shape and composition. The core component of the present disclosure may optionally be assembled with other metal pieces and / or ceramic components. In one embodiment, the core component and any other optional components can be used in the core portion of a ceramic mold, such as those used in the manufacture of superalloy turbine blades for jet aircraft engines. The mold may then be trimmed and the molten superalloy may be poured into a mold cavity having a contact with the metal part. The mold part may be removed from the mold using a combination of mechanical and chemical processes. The ceramic material can be leached with a caustic solution at high temperature and / or high pressure. The beveled core component may then be chemically etched away from the formed superalloy component using acid treatment. In one aspect, the beveled core part is sintered rather than melted. This can increase the number of options for removing the beveled core part. For example, in some cases, the sintered (incompletely fused) metal can be removed using physical means (eg, vibrating). Furthermore, the sintered material can be more easily removed using acid etching in which the etchant penetrates more rapidly through the sintered powder structure.

  4-8 illustrate a method of manufacturing a cast part 414 using a mold 400 according to some aspects of the present disclosure. For example, referring to FIG. 4, the mold may include a first metal part 402 and a second metal part 404. Optionally, the mold 400 may also include an outer shell mold (not shown) that surrounds at least a portion of the first metal part 402 and the second metal part 404. In one aspect, the mold 400 can be used for casting jet aircraft components, such as single crystal superalloy turbine blades.

  Still referring to FIG. 4, the first metal part 402 and the second metal part 404 can be formed using the additive manufacturing techniques described above in connection with FIGS. For example, the first metal portion 402 and the second metal component 404 can be formed simultaneously using additive manufacturing. Alternatively, the first metal part 402 and the second metal part 404 may be formed separately. In one aspect, the first metal component 402 and the second metal component 404 can be formed using the same manufacturing technique (eg, additive manufacturing). Additionally and / or alternatively, the first metal part 402 and the second metal part 404 can be formed using different manufacturing methods.

  If an outer shell mold (not shown) is included, the outer shell mold may be formed around the first metal part 402 and the second metal part 404. Alternatively, the first metal part 402 and the second metal part 404 may be placed in the outer shell mold.

  The first metal part 402 may include a metal having a melting point lower than that of the second metal part 404. In an exemplary embodiment, the first metal component includes a melting point that includes, but is not limited to, at least one of aluminum, nickel, cobalt, chromium, copper, gold, and / or silver, or combinations or alloys thereof. May contain low metals and / or alloys. In another exemplary embodiment, the second metal component 404 includes a refractory metal and / or including but not limited to at least one of molybdenum, niobium, tantalum, and / or tungsten, or combinations or alloys thereof. Alternatively, a heat resistant alloy may be included. These exemplary embodiments are not intended to be limiting. For example, the first metal component 402 can include any metal having a lower melting point than the metal used for the second metal component 404. Similarly, the second metal component 404 can include any metal having a higher melting point than the metal used in the first metal component 402.

  In one aspect, the metal of the first metal part 402 and / or the metal of the second metal part 404 is optionally selected to diffuse one or more elements or alloys within the superalloy part, thereby providing The composition may be changed locally.

  The shape of the second metal part 404 includes cooling holes 416a, 416b (shown in FIG. 8) on the wall of the turbine blade 414 and cooling holes (not shown) that are non-linear and cannot be seen through. 3 illustrates how a core component can be used to form a substrate. The first metal part 402 and / or the second metal part 404 may be used to form cooling holes, trailing edge cooling channels, or microchannels in the cast part. Further, the first metal part 402 and / or the second metal part 404 can be used in a core support structure, a platform core structure, or a tip flag structure.

  The refractory metals molybdenum, niobium, tantalum, and tungsten can be used in accordance with the present disclosure and are commercially available in the form already used in hybrid core components. Some refractory metals may oxidize or melt in the molten superalloy. The refractory metal core component may be coated with a ceramic layer for protection. Alternatively, the second metal component 404 may have a graded transition layer to the surface with a ceramic layer of 0.1-1 mil thickness for protection. The protective ceramic layer may include silica, alumina, zirconia, chromia, mullite, and hafnia.

  The first metal part 402 and / or the second metal part 404 has a graded transition layer, up to a noble metal (ie platinum), or another metal layer such as chromium or aluminum, for protection from oxidation. Also good. These metal layers may be used alone or in combination with the ceramic layers described above.

  Further, the second metal component 404 may include a material that forms a surface protective film when heated. For example, MoSi2 forms a protective layer of SiO2.

  As shown in FIG. 5, the first metal layer 402 can be removed from the mold 400 to form a cavity 406 that is at least partially defined by the second metal component 404. In the example shown in FIG. 5, the cavity 406 is formed in the second metal component 404. In one aspect, the first metal part 402 can be removed from the mold 400 by melting the first metal part 402. In an exemplary embodiment, the first metal part 402 may be selected such that the melting point of the first metal part 402 is lower than the melting point of the second metal part 404. In this way, the first metal part 402 can be melted and removed without melting the second metal part 404 or causing damage to the second metal part 404.

  A liquid metal 408 may be poured into the cavity 406 as shown in FIG. The liquid metal 408 may be a liquid superalloy. For example, the liquid metal 408 may include a nickel-base alloy, particularly including inconel. The liquid metal 408 can be solidified to form a solidified metal 410 as shown in FIG.

  After forming the solidified metal 410, the second metal part 404 may be removed to expose the cast part 414, as shown in FIG. The removal of the second metal component 404 can be performed by chemical means (for example, etching and / or acid treatment). The second metal component 404 can be removed using chemical means that does not remove the solidified metal 410 and does not cause damage to the solidified metal 410. When used as part of the mold 400, the outer shell mold (not shown) can be removed by mechanical means such as crushing. The outer shell mold may be removed before the second metal part 404 or after the second metal part 404.

  The first metal part 402 and the second metal part 404 may be removed during and / or after formation of the superalloy cast part. The first metal part 402 may be selected such that the first metal part 402 has a lower melting point than the second metal part 404. In this way, the first metal part 402 can be melted and removed without melting the second metal part 404 and / or causing damage to the second metal part 404. Thereafter, the molten superalloy may be poured into the cavity formed by removing the first metal part 402 and leaving the second metal part 404. After the molten superalloy is solidified, the second metal part 404 may be removed to produce a cast part (eg, a turbine blade). For example, the second metal component 404 can be removed using chemical means, which includes, but is not limited to, etching using acid treatment. The etching for removing the second metal part may be performed before or after the immersion in the caustic solution at high temperature and high pressure in order to remove any ceramic. In one aspect, the second metal component 404 may be sintered rather than melted. This may increase the number of options for removing the second metal part 404. For example, in some cases, the sintered (incompletely fused) second metal can be removed using physical means (vibrating, etc.). Furthermore, the sintered material can be more easily removed using acid etching where the etchant penetrates the sintered powder structure more rapidly.

  In the above example, the metal that is the first metal part 402 may be used as a disposable mold material, similar to the wax in the lost wax process for forming the turbine blade. Further, the first metal component 402 may be used together with the second metal component 404 in the lost wax method. In this case, both metal parts form part of the casting core. Thereafter, the casting core may be surrounded by wax and, optionally, a ceramic shell. The wax may be removed, and the first metal component 402 may be melted away by the same heating step as the heating step used to remove the wax, or by a different heating step. The first metal part 402 may be used as a gate material in a casting process that provides a passage for a material that is subsequently formed after being melted away.

  This written description uses examples, including preferred embodiments, to disclose the invention and to enable any person skilled in the art to make and use any device or system and perform any incorporated methods. In other words, the present invention can be implemented. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. If such other examples have structural elements that do not differ from the language of the claims, or have equivalent structural elements that do not substantially differ from the language of the claims, It is intended to be included in the scope of Those skilled in the art will be able to add in accordance with the principles of this application by combining and adapting aspects from the various described embodiments, and other known equivalents of each of those aspects. Specific embodiments and techniques may be configured.

12 build plate 14 surplus powder container 30 reservoir assembly 32 discharger 38A trough 38B trough 38C trough 38D trough 38E trough 60 part 62 part 64 part 100 equipment 114 build plate 116 recoater arm 120 laser 122 part 126 reservoir 128 waste container 132 galvo Scanner 136 Energy beam 400 Mold 402 First metal part 404 Second metal part 406 Cavity 408 Liquid metal 410 Solidified metal 414 Casting part 416a Cooling hole 416b Cooling hole

Claims (19)

A mold comprising a casting core comprising a first metal part and a second metal part,
The first metal part has a lower melting point than the second metal part;
A mold wherein the second metal part surrounds at least a portion of the first metal part and defines a cavity in the casting core when the first metal part is removed.   The mold according to claim 1, wherein the first metal component comprises at least one of aluminum, nickel, copper, gold, or silver.   The mold of claim 1, wherein the first metal part comprises an alloy.   The mold according to claim 1, wherein the second metal part comprises tungsten or a tungsten alloy.   The mold according to claim 1, wherein the second metal part comprises molybdenum or a molybdenum alloy.   The mold of claim 1, further comprising an outer shell mold surrounding at least a portion of the casting core.   The mold of claim 6, wherein the outer shell mold comprises a ceramic.   The mold of claim 1, wherein the second metal part is configured to define one or more cooling features in the mold.   The mold according to claim 1, wherein the casting core comprises one or more ceramic parts. A method for producing a cast part, comprising:
Removing a first metal part from a mold assembly comprising a first metal part and a second metal part to form a cavity in the mold assembly, wherein the first metal part has a lower melting point than the second metal part; Having, removing,
Pouring molten metal into at least a portion of the cavity to form a cast part;
Removing the second metal part from the cast part.   The method of claim 10, wherein the first metal component comprises at least one of aluminum, nickel, copper, gold, or silver.   The method of claim 10, wherein the first metal part comprises an alloy.   The method of claim 10, wherein the second metal part comprises tungsten or a tungsten alloy.   The method of claim 10, wherein the second metal part comprises molybdenum or a molybdenum alloy.   The method of claim 10, wherein the mold assembly further comprises an outer shell mold that is removed after molten metal is poured into at least a portion of the cavity.   The method of claim 15, wherein the outer shell mold comprises a ceramic.   The method of claim 10, wherein removing the second metal component comprises at least one of etching or acid treatment.   The method of claim 10, wherein removing the first metal part comprises melting. A method comprising additionally forming a first metal part and a second metal part layer by layer,
(A) irradiating the powder layer of the powder bed to form a fused region;
(B) providing a subsequent powder layer on the powder bed;
And (c) repeating steps (a) and (b) using two or more different powder compositions corresponding to at least the first metal part and the second metal part. Method.